Retinal lipofuscin accumulates with age in the retinal pigment epithelium (RPE), where its fluorescence properties are used to assess
retinal health. It was observed that there is a decrease in
lipofuscin fluorescence above the age of 75 years and in the early stages of
age-related macular degeneration (AMD). The purpose of this study was to investigate the response of
lipofuscin isolated from human RPE and
lipofuscin-laden cells to visible light, and to determine whether an abundant component of
lipofuscin,
docosahexaenoate (DHA), can contribute to
lipofuscin fluorescence upon oxidation. Exposure of
lipofuscin to visible light leads to a decrease in its long-wavelength fluorescence at about 610 nm, with a concomitant increase in the short-wavelength fluorescence. The emission spectrum of photodegraded
lipofuscin exhibits similarity with that of oxidized DHA. Exposure of
lipofuscin-laden cells to light leads to a loss of
lipofuscin granules from cells, while retaining cell viability. The spectral changes in fluorescence in
lipofuscin-laden cells resemble those seen during photodegradation of isolated
lipofuscin. Our results demonstrate that fluorescence emission spectra, together with quantitation of the intensity of long-wavelength fluorescence, can serve as a marker useful for
lipofuscin quantification and for monitoring its oxidation, and hence useful for screening the retina for increased oxidative damage and early AMD-related changes.